制冷用木屑基质复合吸附剂的制备及性能测试

Preparation and performance testing of sawdust based composite adsorbents for refrigeration

为开发出用于吸附式制冷的高性能吸附剂,基于炭化造孔原理制备了木屑氯化钙复合吸附剂,测试了氨气作为制冷剂的吸附性能,考察了原料配比、炭化温度对复合吸附剂性能的影响,并利用扫描电镜和能谱分析仪观察了复合吸附剂的微观形貌和元素分布。结果表明:炭化法制备的复合吸附剂具有丰富的微孔结构,氯化钙的含量高,达到70%以上,而且氯化钙在样本吸附剂中分布均匀;样本吸附剂的烧失率随炭化温度的升高而增加,而样本的吸附量随着炭化温度的升高先增大后减小;样本中氯化钙的含量对吸附量具有重要的影响。样本SB4的最大单位质量吸附剂制冷功率(SCP)达到1418.16 W/kg,前10 min的平均SCP达到876.1 W/kg。实验结果表明,炭化法制备的复合吸附剂不仅解决了氯化钙吸氨过程中的膨胀结块现象,而且增加了传质速率。

To develop a high performance adsorbent, sawdust-CaCl2 composite adsorbents were prepared by carbonization, and their adsorption performance were assessed by measuring the variation of pressure in a vessel with a known volume, with NH3 as the refrigerant. The effects of raw material ratio, carbonization temperature on the adsorption performance of the prepared sawdust-CaC12 composite adsorbents were investigated. The composite adsorbents were characterized by scanning electron microscope （ SEM ） and X-ray energy dispersive spectroscopy. The results show that, the prepared composite adsorbents have rich microporous structure, with CaCI2 content as high as 70%. Besides, CaC12 and the sawdust mixed uniformly. The bum-off of the sample augments with the increase of carbonization temperature, and the NH3 adsorption quantity increases first and then decreases with the increase of carbonization temperature. Compared with the carbonization temperature, the raw material ratio plays the dominant influence on the adsorption properties of the samples. The maximum specific cooling power reaches 1418.16 W/kg, and average specific coolingpower reaches 876.1 W/kg with the cycle duration of 10 minutes. The present study demonstrates thatthe sawdust-CaCl2 composite adsorbents prepared by carbonization are free of salt swelling and agglomeration, and provide a better mass transfer performance.